Colorectal cancer (CRC) is the third most common cancer in both men and women and accounts for 9% of all new cancer cases and cancer deaths in the United States (1). Upon diagnosis, 19% of CRC cases are metastatic and while the overall 5-year survival rate for patients with CRC is 65%, in metastatic disease it is only 12% (1). Emerging evidence demonstrates that tumor progression involves complex heterotypic multicellular interactions between cancer cells and tumor-associated mesenchymal cells (2). CRC is often accompanied by a well-orchestrated desmoplastic reaction, which involves the distant recruitment of bone marrow-derived mesenchymal stem cells (BM-MSC) in growing tumors. BM-MSC have the potential to differentiate into multiple cell lineages such as osteoblasts, chondrocytes and adipocytes (3). Mouse models reveal that BM-MSC migrate to colon tumor xenografts (4, 5) and are precursors of tumor-associated mesenchymal cells (6-8), which in turn stimulate cancer progression (9, 10). The tropism of MSC for tumors is thought to recapitulate their migration into wounds during wound healing and tissue repair (11, 12).
The human epidermal growth factor receptor (HER/ErbB) tyrosine kinases (RTKs) and their ligands are involved in cancer cell proliferation, survival, motility, invasion and metastasis. The following four HER receptors have been described in mammals: HER1 (ErbB1 or epidermal growth factor receptor [EGFR], HER2 [ErbB2 or neu], HER3 [ErbB3], and HER4 [ErbB4]). Activation of these receptors can occur by the following three different mechanisms: interaction with specific HER ligands, overexpression of the receptor, and molecular alterations such as point mutations or truncations. It is through dimerization and transphosphorylation that HER receptors perform their signaling functions. About 80% of all CRCs exhibit HER1 expression or overexpression correlating with increased metastasis and reduced patient's survival (13, 14). It has been indicated that HER3 expression is involved in CRC progression and that its phosphorylation is of prognostic value (15-17).
The neuregulin (NRG) family of growth factors comprises numerous heparin-binding glycoproteins that arise via alternative splicing off four distinct genes (NRG-1, NRG-2, NRG-3, and NRG-4). NRG-1 and NRG-2 are the most closely related: both interact with HER3. NRG-1 has a high binding affinity for HER3 and preferentially acts through HER2-dependent recruitment of PI3K (18-20). Alternative splicing and regulation through multiple promoters produce at least 15 different NRG-1 isoforms; most are synthesized as transmembrane precursors and released as soluble factors by action of cell surface proteases, such as tumor necrosis factor-alpha converting enzyme (TACE) (21, 22). NRGs are produced by epithelial cells in melanoma, breast and ovarian tumors (23, 24), but also by tumor-associated mesenchymal cells in gastric and breast tumors (25-27). US 2007/0275404 and Eschrich et al. (28) disclose that expression of the NRG-2 gene might be used as a prognostic marker for breast and colorectal cancer, respectively.
Yoshioka et al. (29) further disclose that NRG-1 (heregulin) might participate in a highly liver metastatic phenotype of a human colon cancer cell line via HER2/HER3 signalling. Liles et al. (30) disclose that fibroblast-derived NRG-1 promote proliferation of a pancreatic cancer cell line via phosphorylation of HER3 and that said proliferation can be best disrupted through combined HER1 (EGFR)-HER3(erbB3) inhibition. Venkateswarlu et al. (Oncogene 2002: 78-86) disclose that autocrine heregulin is responsible for cell cycle re-entry of colon cancer cells and that heregulin neutralizing antibody treatment generates apoptosis of the latter cells. Tatsuguchi et al. (Gastroenterology 2011, vol 140 No 5 suppl 1: S340) further disclose that significantly higher expression levels of heregulin are found in CRC tissue samples (i.e. predominantly in the cytoplasm of cancer cells) compared to normal tissue counterparts and concludes that heregulin may be a useful marker of prognostic significance in CRC patients. Yonezawa et al. (Gastroenterology 2004, vol 126 No 4 suppl 2: A263) disclose that heregulin overexpression was immunohistochemically observed in cancer cells and mesenchymal cells and that heregulin might regulate VEGF secretion through autocrine and paracrine mechanisms. However, no correlation has been described or suggested between high expression of transmembrane heregulin in solely mesenchymal cells and a worse prognosis.
About 19% of CRC patients present initially with metastatic disease and the standard chemotherapy regimen for these patients are the chemotherapeutic agents 5-fluorouracil, irinotecan, and oxaliplatin, often in combination with the monoclonal antibodies cetuximab or panitumumab (31, 32) (NCCN Clinical Practice Guidelines in Oncology. Colon Cancer. Version 3.2011). Cetuximab and panitumumab bind to HER1 (EGFR) on cancer cells, thereby blocking the downstream intracellular signaling pathways. One member of this cascade is KRAS, and over the recent years increasing evidence suggested that patients with KRAS mutations do not benefit from the addition of cetuximab or panitumumab to standard chemotherapy (33). KRAS mutations are found in approximately 40-60% of all CRC specimens. As a consequence, KRAS testing is mandatory for patients with metastatic CRC before receiving cetuximab or panitumumab (33).
Pertuzumab is a recombinant, humanized mAb that specifically binds HER2 (34) and prevents HER2 homo- and HER2/HER3 heterodimerisation (35). Because of this mechanism of action, pertuzumab antitumor activity is not restricted to tumors with HER2 overexpression and therefore differs from the therapeutic monoclonal antibody trastuzumab, which binds to a non-overlapping juxtamembrane region of HER2's extracellular domain and cannot inhibit HER2/HER3 heterodimerisation. In addition, a phase I/II clinical trial is currently ongoing in Canada and the United States to study the effectiveness of pertuzumab combined with cetuximab in patients with locally advanced or metastatic CRC who did not respond to cetuximab (36).
The present invention discloses that increased levels of transmembrane type 1 neuregulin-1 in tumor-associated mesenchymal cells in a sample of human colorectal cancer patients surprisingly and significantly correlate with a worse prognosis of said patients in terms of tumor stage, invasion depth and 5-year progression-free survival. The latter prognosis further indicates that these patients would benefit from a therapy based on the prevention of neuregulin-1 and/or HER3 activity. The latter prognosis is thus valuable to fine tune therapy of colorectal cancer by predicting whether a patient would benefit from a combined treatment of—for example—pertuzumab with cetuximab and/or whether a patient has resistance to HER1 inhibitors such as cetuximab.